# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a331412 Showing 1-1 of 1 %I A331412 #21 Jan 18 2020 11:07:58 %S A331412 8857357509,10783550414,15197873690,23620285689,25537083494, %T A331412 34736070369,60326914934,64139567205,73969772954,75776483145, %U A331412 77509981185,83968675790,93092467754,100012014465,112236593469,113606741534,116519300534,118905484334,132584489114,134889106065 %N A331412 Unitary abundant numbers k such that k + 1 is also unitary abundant. %C A331412 Apparently most of the terms are squarefree. Up to 10^13 there are 1150 terms, for only 17 terms k either k or k + 1 is nonsquarefree, and there are no terms k such that both k and k + 1 are nonsquarefree. The first nonsquarefree term is a(32) = 285491549265. %H A331412 Giovanni Resta, Table of n, a(n) for n = 1..1150 (terms below 10^13) %e A331412 8857357509 is a term since usigma(8857357509) = 17766604800 > 2 * 8857357509, and usigma(8857357510) = 17851083264 > 2 * 8857357510, where usigma is the sum of unitary divisors function (A034448). %Y A331412 Cf. A034448, A034683, A292704. %Y A331412 Analogous sequences: A096399 (regular abundant), A283418 (primitive), A318167 (bi-unitary), A327635 (infinitary), A327942 (nonunitary). %K A331412 nonn %O A331412 1,1 %A A331412 _Amiram Eldar_ and _Giovanni Resta_, Jan 18 2020 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE